1. Field of Invention
The invention is directed to valves for compensating for pressure changes within an annulus of an oil or gas wellbore.
2. Description of Art
Valves can be used in oil and gas well completions to facilitate displacement of drilling fluids, such as drilling mud, out of the well by pumping completion fluids down the wellbore. In general, these valves allow the completion fluid to be pumped down the wellbore causing the drilling fluid within the wellbore annulus to flow into the valve and, thus, a tubular string containing the valve, and then upward within the tubular string to the surface of the well.
Wellbore barriers such as packers, bridge plugs and the like are used to seal or isolate zones or areas of an annulus of wellbores. In general, the wellbore barriers are disposed within a wellbore above and below a “zone” or area of the wellbore in which production, or other wellbore intervention operations are performed. In some instances, the isolated zone is not being produced or intervention operations are not being performed, however, tubing, e.g., an inner casing, is disposed through this zone so that oil or gas production or other downhole operations can be performed below the isolated zone. In these instances, the fluid trapped or sealed in this isolated zone can expand do to increases in the temperature of the fluid trapped in the isolated zone. When the temperature increases, such as during production from other zones within in the wellbore, the fluid expands and can cause damage to the inner casing of the wellbore, the outer casing of the wellbore, other components within the wellbore, or the formation itself. To reduce the likelihood of such damage, devices to relieve the pressure in the isolated zone are employed.